Species‐specific flowering cues among general flowering Shorea species at the Pasoh Research Forest, Malaysia

Abstract

1. In a unique phenomenon restricted to the ever wet forests of Southeast Asia, hundreds of species from dozens of plant families reproduce synchronously at irregular, multi-year intervals. The proximate environmental cues that synchronize these general flowering events have not been evaluated systematically because there have been no long-term, high temporal resolution, species-level records from the region.2. We present 13 years of weekly flowering records for five Shorea species as well as daily temperature and rainfall records from the Pasoh Forest Reserve, Peninsular Malaysia. We constructed models to evaluate hypothesized relationships between flowering and cool temperature, drought, and additive and synergistic effects of cool temperature and drought for each species. Model parameters include periods of time for floral cue accumulation and flower development and temperature and/ or rainfall thresholds required for floral initiation. Parameters estimated using flowering observations from 2001 to 2011 were used to forecast flowering for 2011-2014. 3. We show that drought and cool temperatures acting synergistically best explain the timing of flowering events for all Shorea species in the section Mutica and forecast the largest general flowering event accurately. Periods estimated for signal accumulation ranged from 54 to 90 days among species. Periods estimated for flowers to develop ranged between 43 and 96 days and closely followed the interspecific sequence of flowering in the Shorea species. Drought and temperature thresholds also varied among species, with Shorea maxwelliana requiring the most severe drought and Shorea leprosula the lowest temperatures. 4. Synthesis. Our results indicate that cool temperatures and low rainfall occurring on seasonal time-scales of about 2-3 months rather than brief cold snaps or brief droughts best explain general flowering in Shorea species at the Pasoh | 587 Journal of Ecology CHEN Et al.

Drought and cool temperature cue general flowering synergistically in the aseasonal tropical forests of Southeast Asia

“…Five Shorea species in family Dipterocarpaceae were selected previously to develop mechanistic models considering the relationship between flowering and environmental triggers (Chen et al, ). Shorea macroptera, Shorea parvifolia, Shorea acuminata and S. leprosula are in section Mutica , a group which shows high loyalty to general flowering (Appanah, ).…”

“…Sample sizes are 10, 10, 13, 35 and 23 individuals for S. macroptera, S. parvifolia, S. acuminata, S. leprosula and S. maxwelliana , respectively. The method for data collection was described in Chen et al ().…”

“…[ X ] + is equivalent to max{ X , 0}. We follow the modeling framework of Chen et al () to maintain n d as the period of flower development during which environmental signals play no role to influence floral induction.…”

“…Chen et al () concluded that drought and cool temperatures acting synergistically best explain the timing of flowering events for all Shorea species in the section Mutica . We examined the robustness of this conclusion by assessing the relationships between flowering intensity, , , and the synergistic effect of cool temperature and drought by constructing four different models.…”

“…Here we developed models considering WD and API as drought indices that affect flowering. We compared the predictive performance of different drought indices using the flowering phenology data in Chen et al (). Our analyses confirmed that the synergistic model that considers both cool temperature and drought performs the best regardless of the choice of drought indices for most Shorea species studied.…”